PTD 1 discloses a power conversion device including first and second semiconductor modules. Each of the first and second semiconductor modules includes a switching element first and second external terminals, and a diode connected between the first and second external terminals for detecting the temperature of the switching element. The switching elements of the first and second semiconductor modules are connected in parallel with each other.
The first external terminal of the first semiconductor module receives constant current from a constant current source the second external terminal of the first semiconductor module is connected to the first external terminal of the second semiconductor module through a wiring pattern, and the second external terminal of the second semiconductor module receives a ground potential. The voltage between the first external terminal of the first semiconductor module and the second external terminal of the second semiconductor module changes according to the average temperature of the switching elements of the first and second semiconductor modules. When the average temperature exceeds a threshold temperature, current flowing through the switching elements is reduced, and overheat of the switching elements is prevented.